This invention relates in general to armature assemblies and deals more particularly with an improved armature assembly having a spline drive which provides positive radial connection and axial freedom relative to an associated spline shaft.
The armature assembly of the present invention is particularly adapated for use in an electromagnetically actuated clutch or brake mechanism. Such a mechanism essentially comprises two parts. One part, an annular electromagnet assembly, attracts the other part, an armature assembly, when electrical current is applied to a coil associated with the electromagnet assembly. The electromagnet assembly is or may be faced with friction material to absorb heat and retard wear. When one of the aforesaid two parts is mounted in fixed position, the system functions as a brake. However, if both parts are free to rotate the system operates as a clutch, which may, for example, comprise part of a drive transmission system. A magnetic field is generated when current flows through the magnet coil, which draws the armature assembly into direct contact with the electromagnet assembly. The strength of the magnetic field is directly proportional to the amount of current applied to the coil.
In a system of the aforedescribed general type, the armature assembly includes an armature plate, a splined hub bolted or otherwise fastened to the plate and fan blades carried by the plate. However, fastening the hub and/or the fan blades to the armature plate can cause warpage of the plate.
It is generally desirable that the hub be made from material softer than the material of the splined shaft to which it is attached to reduce risk of damage to the shaft resulting from heavy shock loads or the like. Such damage as may occur will usually be confined to the armature assembly which may be replaced more easily and at less expense than the shaft. However, axial movement of the relatively soft hub on the harder shaft often causes wear and fretting resulting in loosening of the armature assembly and vibration or chattering within the system accompanied by an increase in operational noise level. The occurrence of mechanical failure between the hub and the armature plate is often accompanied by abrupt loss of driving connection between the armature assembly its associated shaft. The result may be a total loss of braking power or coupling connection within an associated system.
The present invention is concerned with the aforedescribed general problems.